Refrigerating apparatus



s. H. cowlN V Sept. 8, 1936.

REFRIGERATING APPARATUS Filed April 18, 1954 2 Sheets-Sheet l Sept. 8,1936. s. H. cowm 2,053,945

REFRIGERATING APPARATUS Filed April 18, 1954 2 Sheets-Sheet 2 W gvENTOR:

BY 2 uni??? Patented Sept. 8, 1 936 BEFBIGERATING APPARATUS Stuart H.Cowln, Dayton, Ohio, assignor to Gen eral Motors Corporation, Dayton,Ohio, a corporation of Delaware Application April 18, 1934, Serial No.721,183

8 Claims.

This invention relates to refrigeration and more particularlyto theconditioning of air.

An object of this invention is to provide a method and apparatus forconditioning air in a manner to balance the varying heat absorption fromthe air with the heat dissipation, from the system, and to overcome thetendency to produce detrimentally low temperatures in the air coolingdevices or zones when the total refrigeration load is relatively small,or where one or more of a plurality of air conditioning zones areinactive.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Fig. l is a diagrammatic representation of an apparatus embodyingfeatures of my invention; and

Fig. 2 is a cross-sectional view of a type of pressure regulating valvewhich may be used in the suction line.

In practicing my invention, the air in one or more compartments orspaces It, Ii and i2 is conditioned by the cooling action of one or moreevaporators or evaporating zones l3, l4 and I5 where heat absorptionfrom the air, or refrigeration load, .varies from time to time. Therefrigerant evaporated in these evaporators is conveyed to refrigerantliquefying unit l6 where the heat dissipation from the system tendsnormally to be constant. Here the refrigerant is liquefied and isreturned through the liquid refrigerant line I! to the evaporators. Theevaporated refrigerant is conveyed from the evaporators to the unit I 6through the suction line or connection I8. The refrigerant liquefying orcompressor unit It may include a compressor I 9, a condenser 20, liquid,refrigerant receiver 2|, and a motor 22 which drives the compressor It.

In an air conditioning method or apparatus of this kind, not only thetotal refrigeration load from all of the evaporating zones is likely tovary widely from time to time, but the individual load on any oneevaporating zone is also quite likely to vary widely. The volumetriccapacity, and hence heat dissipating power, of compressor IS, on theother hand tends to be constant because of the constant speedcharacteristics of the more desirable modern motors. Thus complicationsresult unless means are provided to balance the constant volumetriccapacity or heat REISSUED dissipating power of the compressor unit withthe varying refrigeration demands upon the system. When therefrigeration demands are relatively small, the compressor unit tends toreduce the refrigerant temperatures in the evap- 5 orators to the pointwhere moisture from the ,air' freezes on the evaporators and eventuallyclogs them. Also there is a tendency for the suction lines to becomefrosted because of unavoidable suction of liquid refrigerant from the 10evaporators. It is to the avoidance of these and other undesirableresults that this invention is directed.

Means are provided for compensating or balancing the constant volumetricof heat dissipating capacity of the unit l6 while it is operating withthe varying heat absorption or evaporation in the evaporators l3, l4 andi5. To this end, heat absorption or automatic pressure limiting means inthe form of valve 23 is in the suction passage [8 which automaticallylimits the fall in pressure in the suction con-' nection I8 adjacent theevaporators and prevents the refrigerant vapor pressure or temperaturein the evaporators from falling suflicient- 1y low to cause freezing ofmoisture from the air on the evaporators. Also means are provided forcontrolling the flow of refrigerant to the variousevaporators inaccordance with the refrigerationdemands of the air in the various 0spaces. Thus the flow of liquid refrigerant from the line IT to theevaporators l3, l4 and I5 is controlled by means of automatic expansionvalves 24, 25 and 26 each of which tends to feed liquid refrigerant intothe evaporators when the pressure therein falls below a predeterminedlimit. Thermostatic bulbs 21, 28, and 29 are placed in the connections30, 3| and 32 from the outlets of the evaporators to the suction linei8. These thermostatic bulbs throttle the valves 24, 25 and 26 wheneverthe liquid refrigerant in the evaporators tends to spill over into the.suction line. In addition, thermostatic controls in the form ofthermostatic switches 33, 34 and 35 are placed near the air inlets tothe air conditioners 36, 31 and 38 where the air is representative ofthe air in the compartments it, ii and I2 respectively. Thesethermostatic switches control the flow of refrigerant in the respectiveevaporators and control the operation of the compressor through themotor 22, causing it to stop when all of said switches are open and tostart when one or more of the switches are closed. This is accomplishedby placing solenoid valves 39, 40 and 4| adjacent valves 24, 25 and 55placed 20 fl. These solenoid valves prevent flow of liquid refrigerantinto the respective evaporators when the temperature in the respectivespaces to, H and I2 falls below a predetermined limit, and permit theflow of liquid refrigerant into the evaporators when that temperaturerises above a predetermined limit. In addition, the switches ll, 34 andII control the operation of the compressor I8 and are thereforeconnected to the relay 4! so that the contact 43 is opened when all ofthe thermostatic switches are open and is closed when any one of theswitches is closed. The relay 4! controls the starting and stopping ofmotor 22 and compressor ii.

In addition, motor driven blowers 44, 4! and N, which cause thecirculation of air over the evaporators are controlled by means ofmanual switches 41, 48 and 49, which switches are in series with thethermostatic switches 33, 34 and 38 so that anyone air conditioner, andall its functions, may be cut in or out by closing or opening itsrespective manual switch.

The air conditioners I8, 31 and ll may be of any type desired. In thisparticular embodiment, they may take the form of vertical casings havingair inlets Ill, ii and 52 at the bottom, where the air flow is indicatedby arrows, and having air outlets 53, I4 and I at the top above blowersll, and It. The evaporators l3, l4 and II are placed within the casingsas will be readily apparent from the drawings. Drain pans I, 51, I. areplaced at the bottom of casing to catch any moisture condensed on theevaporator.

Fig. 2 shows a type of valve which may be used in the suction line i8and which is diagrammatically represented at 23 in Fig. 1. Refrigerantfrom the evaporators enter the check valve 23 at the inlet and leavethrough the outlet Bl from whence they continue to the compressor. Thevalve structure 23 includes valve seats 62 and 63 upon which thebalanced valves 84 and 65 seat. These valves are mounted on a stem '6upon which a bellows 81 is secured. The bellows 01 is also secured tothe casting it so that the interior of the bellows is subjected to anyconstant pressure such as atmospheric pressure. The bellows is alsoprovided with an adjustable spring 89 which may be adjusted by means ofthe screw III to calibrate the valve. Passages H are provided so thatthe outside of the bellows is subjected to the evaporator pressure. Asthe pressure is decreased the bellows is expanded and thus tends tothrottle or close the valves.

The stem 66 may be octagonal in cross-section with the sides ll of theoctagon tapering toward each end of the stem. This provides a relativelysmall bearing surface at the center of the stem to permit free play atboth ends of the stem.

In operation, the refrigerant liquefying unit It is started whenever anyone or more of the switches 33, 34 or 35 are closed by rise intemperature in that environment. If the refrigerating load imposed onthe one or more evaporators happens to be the same as the heatdissipating capacity of the unit I, the valve 23 opens fully and permitsthe compressor 19 to withdraw refrigerant from the active evaporator orevaporators to its full capacity. However, if therefrigerating loadimposed on the active evaporators diminishes, due to low outsideatmospheric'temperatures, or because one or more of the evaporators arerendered automatically or manually inactive, the load is quite likelynot to balance with the normal heat dissipating ca pacity of the unitll. Under these conditions,.

if it were not for action of valve ll, the unit It would reduce thevapor-pressure, and hence the temperature, of the liquid refrigerant inthe active evaporators to the point where moisture from the air would befrozen on the surfaces of the evaporators. If this would occur, the re--frigeration load would be further decreased by the reduced flow of airthrough the ice clogged passages and thus the undesirable conditionwould be aggravated. With the valve 23, on the other hand, the flow ofrefrigerant to the compressor, and hence the heat dissipating capacityof the compressing unit I 8. is throttled or limited to the extent thatit cannot reduce the vapor-pressure and temperature of the refrigerantin the evaporators to a point where moisture from the air would befrozen on them. Thus proper temperatures are maintained on the aircooling surfaces of the apparatus so that air may be properly cooled andmoisture may even be condensed, but not frozen, on them regardless ofthe variance between the heat absorption by the evaporators and thenormal heat dissipating capacity of the compressor unit. An eflicientand satisfactory mode of conditioning air is thus provided.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. An air conditioning apparatus comprising a compressor, a motordriving said compressor, a condenser connected to said compressor, aplurality of air conditioning evaporators connected to said condenser, asuction connection between said evaporators and said compressor, adevice responsive to a psychrometric function of air controlling theevaporation of refrigerant in one of said evaporators, and meansautomatically limiting the quantity of refrigerant compressed by saidcompressor while operating to prevent said compressor from producing avapor pressure in said evaporators sufliciently low to cause freezing ofmoisture on said evaporators.

2. An air conditioning apparatus comprising a compressor, a motordriving said compressor, a condenser connected to said compressor, ablower for each evaporator, a plurality of air conditioning evaporatorsconnected to said condenser, a suction connection between saidevaporators and said compressor, a device responsive to a psychrometricfunction of air controlling the evap-. oration of refrigerant in one ofsaid evaporators, and means automatically limiting the quantity ofrefrigerant compressed by said compressor while operating to preventsaid compressor from producing a vapor pressure in said evaporatorssumcientlylow to cause freezing of moisture on said evaporators.

3. An air conditioning apparatus comprising a compressor, a motordriving said compressor, a condenser connected to said compressor, apinrality of air conditioning evaporators connected to said condenser, asuction connection between said evaporators and said compressor, aswitch responsive toa psychrometric function of air for each evaporator,each switch controlling the evaporation of refrigerant in the respectiveevaporator and said switches controlling said motor to cause said motorto stop when all of said switches are open and to start when one or moreof said switches are closed, the means automatically responsive to apsychrometric function of air for 2,053,945 limiting the quantity ofrefrigerant. compressed by said compressor while operating to preventsaid compressor from producing a vapor pressurein said evaporatorssufllciently low to cause freezing of moisture on said evaporators.

4. An air conditioning apparatus comprising a compressor, a motordriving said compressor, a condenser connected to said compressor, aplurality of air conditioning evaporators connected to said condenser, asuction connection between said evaporators and said compressor, aswitch tion connection adjacent said evaporators below a refrigerantvapor pressure sufficiently low to cause freezing of moisture on saidevaporators.

5. An air conditioning apparatus comprising a compressor, a motordriving said compressor, a condenserconnected to said compressor, aplurality of air conditioning evaporators connected to said condenser, asuction connection between said evaporators and said compressor, adevice responsive to a psychrometric function of air controlling theevaporation of refrigerant in one of said evaporators, and an automaticpressure limiting valve in said suction connection limiting the fall inpressure in said suction connection adjacent said evaporators below arefrigerant vapor pressure sufficiently low to cause freezing ofmoisture on said evaporators.

6, The method of conditioning air in'a plurality of air spaces whichcomprises compressing a refrigerant in a compressing zone as long as apsychrometric function, of airin any one of said spacesis above apredetermined limit, condensing said refrigerant and conveying portionsin said air spaces, and limiting the return of rev to evaporating zonesinto thermal exchange with the air in said spaces and thereby causingevaporation, withdrawing evaporated refrigerant from said evaporatingzones and returning it to said compressing zone, controlling the flow ofrefrigerant in said evaporating zones in accordance with a psychrometricfunction of the air frigerant to said compressing-zone while ,com-

pressing refrigerant to maintain the refrigerant 7. 'I he method ofconditioning air in a plurality of air spaces which comprisescompressing a refrigerant in a compressing zone as long as apsychrometric function of the air in any one of said spaces is above apredetermined limit, condensing said refrigerant, conveying portions ofsaid condensed refrigerant for evaporation in evaporating zones inthermal exchange with continuously circulated air in said spaces,controlling the conveyance of said portions in accordance with apsychrometric function of the air in said spaces, withdrawing evaporatedrefrigerant from said evaporating zones and re,-

'- maintain the evaporating pressure in said evaporating zonessuillciently high to prevent freezing of moisture from the air. A

8. The method of conditioning air in a plurality of air spaces whichcomprises compressing a refrigerant in a compressing zone as long as apsychrometric function of the air in any one of said spaces is above apredetermined limit, condensing said refrigerant, conveying portions ofsaid condensed refrigerant for evaporation in evaporating zones inthermal exchange with continuously circulated air in said spaces,controlling the conveyance of said portions in accordance with apsychrometric function of the air in said spaces, withdrawing evaporatedrefrigerant from said evaporating zones and returning it to saidcompressing zone, maintaining normal compressing capacity in saidcompressing zone such that said evaporating zones do not freeze moisturefrom the air, throttling the return of evaporated refrigerant to saidcompressing zone while compressing refrigerant when said evaporatingzones evaporate an amount of refrigerant below the normal compressingcapacity in said compressing zone to I compressing zone inactive whenthe temperatures of the air of said evaporating zones are below theirpredetermined limits.

s'rom'r H.- cowm.

